Creep aging forming(CAF) is a potential process used to manufacture large integral components of magnesium(Mg) alloys. The selected stress plays a crucial role in creep aging processes but the mechanism by which stres...Creep aging forming(CAF) is a potential process used to manufacture large integral components of magnesium(Mg) alloys. The selected stress plays a crucial role in creep aging processes but the mechanism by which stress loading method affects creep aging of Mg alloys is still unclear. In this paper, the microstructural evolution of precipitated phases and precipitation-free zones(PFZ) at grain boundaries with different stress loading modes(unstressed, unidirectional tensile stress, and cyclic stress) at 250 ℃ were investigated along with changes in mechanical properties. The results showed that the addition of stress during aging effectively promoted the precipitation of precipitated phases, while unaffecting grain size. Unidirectional tensile stress caused directional growth of β phase([1010]), as well as rotation of weave towards the basal plane texture, resulting in namely stress orientation effect. Solute atoms diffused in the direction of tensile stress while vacancies moved perpendicular to the direction of tensile stress, resulting in PFZ at grain boundaries(157.06 nm). By contrast, cyclic stresses led to the growth of β phase in three directions([1010], [1100] and [0110]). The solute atoms and vacancies were uniformly distributed in the Mg matrix instead of directional diffusion, effectively reducing the width of PFZ(112.39 nm) at the grain boundary. These features significantly improved the mechanical properties of alloy specimens after cyclic stress creep aging when compared to unidirectional stress creep aging, with yield strength(YS), ultimate tensile strength(UTS), and elongation(EL) enhanced from 171.6 MPa, 305.5 MPa, and 4.4%to 174.8 MPa, 326.3 MPa, and 6.9%, respectively.展开更多
To investigate the role of pre-twins in Mg alloy sheets during warm planar deformation, the stretch forming is conducted at 200 ℃. Results suggest the formability of the pre-twinned AZ31 Mg alloy sheet is enhanced to...To investigate the role of pre-twins in Mg alloy sheets during warm planar deformation, the stretch forming is conducted at 200 ℃. Results suggest the formability of the pre-twinned AZ31 Mg alloy sheet is enhanced to 11.30 mm. The mechanisms for the improved formability and the deformation behaviors during the planar stretch forming are systematically investigated based on the planar stress states. The Schmid factor for deformation mechanisms are calculated, the results reveal that planar stress states extremely affect the Schmid factor for {10-12}twinning. The detwinning is activated and the prismatic slip is enhanced in the pre-twinned sheet, especially under the planar extension stress state in the outer region. Consequently, the thickness-direction strain is accommodated better. The dynamic recrystallization(DRX) type is continuous DRX(CDRX) regardless of the planar stress state. However, the CDRX degree is greater under the planar extension stress state.Some twin lattices deviate from the perfect {10-12} twinning relation due to the planar compression stress state and the CDRX. The basal texture is weakened when the planar stress state tends to change the texture components.展开更多
Mg97−xZn1Y2Alx alloys with long-period stacking ordered(LPSO)structures were prepared by conventional casting method.The optical microscopy(OM),X-ray diffraction(XRD)and the scanning electron microscope(SEM)equipped w...Mg97−xZn1Y2Alx alloys with long-period stacking ordered(LPSO)structures were prepared by conventional casting method.The optical microscopy(OM),X-ray diffraction(XRD)and the scanning electron microscope(SEM)equipped with energy dispersive X-ray spectroscopy(EDS)were used to analyze the microstructure of the alloys with different compositions.Immersion test and electrochemical measurement were used to evaluate the corrosion behavior of the alloys at room temperature,and the corrosive medium is 3.5%NaCl aqueous solution.The results showed that,with the increasing aluminum(Al)addition,exceptα-Mg and LPSO phases,new phases also emerged on the grain boundaries.At the same time,the zigzag part of LPSO phases disappeared,and the boundaries between LPSO phases andα-Mg became smooth.Furthermore,the addition of Al to Mg-Zn-Y alloys could hinder the activity of cathodic hydrogen evolution reaction and improve the uniformity and compactness of the protective surface film,thus,enhanced the corrosion resistance of Mg-Zn-Y alloys.展开更多
Texture evolution of an extruded dilute Mg-1Sn-1Zn-1Al alloy was thoroughly investigated based on the twinning and dynamic recrystallization(DRX)behavior via hot compression at a strain rate of 10 s^(-1)and temperatur...Texture evolution of an extruded dilute Mg-1Sn-1Zn-1Al alloy was thoroughly investigated based on the twinning and dynamic recrystallization(DRX)behavior via hot compression at a strain rate of 10 s^(-1)and temperature of 225℃.It was found that the types and intensities of the texture are strongly dependent on the fraction of twins and DRX modes as well as regions where sub-grain boundaries(sub-GBs)are intensively accumulated.At the initial stage of deformation,the formation of compression direction(CD)-tilted basal texture was mainly determined by the occurrence of{101^(-)2}extension twins.As the strain increases,the variation in the texture intensity was greatly dominated by the DRX modes but the type of main texture remained unchanged.These findings are of great importance for texture modification of wrought Mg-Sn-based alloys during post-deformation.展开更多
The effects of Ti additions(0,0.4,0.6,0.8,1.0,1.2 wt.%)on the microstructure and mechanical properties of as-cast and aging Mg-0.4%Zn-1.0%Zr-1.5%Ca(wt.%)alloys were investigated.The results indicated that minor Ti can...The effects of Ti additions(0,0.4,0.6,0.8,1.0,1.2 wt.%)on the microstructure and mechanical properties of as-cast and aging Mg-0.4%Zn-1.0%Zr-1.5%Ca(wt.%)alloys were investigated.The results indicated that minor Ti can effectively refine grains,while excessive Ti addition resulted in the grain coarsening.When the content of Ti was 0.8 wt.%,the as-cast alloy exhibited the finest grain size of 39μm which contributed to the optimal mechanical properties with Brinell hardness of 57.9 HB,ultimate tensile strength of 145 MPa and elongation of 3.2%.After T6 heat treatment,the continuous net-like Mg_(2)Ca and Mg_(6)Zn_(3)Ca_(2)phases changed to uniform massive T phases(ternary Mg-Zn-Ca phases)and dispersive halo-like precipitates(Mg_(2)Ca and Mg_(6)Zn_(3)Ca_(2)phases).The ultimate tensile strengths of the alloy at room temperature(RT),175℃and 200℃were correspondingly improved to 182 MPa,169 MPa and 141 MPa,respectively.展开更多
The creep properties of as-cast Mg-9Al-1Si alloy and Mg-9Al-1Si-1SiC composite were compared.The results show that Mg-9A1-lSi-lSiC composite performs a better creep resistance than that of Mg-9Al-1Si alloy at constant...The creep properties of as-cast Mg-9Al-1Si alloy and Mg-9Al-1Si-1SiC composite were compared.The results show that Mg-9A1-lSi-lSiC composite performs a better creep resistance than that of Mg-9Al-1Si alloy at constant temperature and stress(473 K,70MPa).Besides,the creep behavior of Mg-9Al-1 Si-1SiC composite at various temperature from 448 K to 498 K and under stresses of 70-90 MPa were systematically investigated.The Mg-9Al-1 Si-1SiC composite exhibited a stress exponent from 5.5 to 6.9 and the creep activation energy fell within the range of 86-111 kJ/mol.The results showed that the creep mechanism of Mg-9Al-1Si-1SiC composite was mainly attributed to the effects of secondary phase strengthening mechanism and dislocation climb mechanism.展开更多
With the development of the times,people’s requirements for communication technology are becoming higher and higher.4G communication technology has been unable to meet development needs,and 5G communication technolog...With the development of the times,people’s requirements for communication technology are becoming higher and higher.4G communication technology has been unable to meet development needs,and 5G communication technology has emerged as the times require.This article proposes the design of a low-noise amplifier(LNA)that will be used in the 5G band of China Mobile Communications.A low noise amplifier for mobile 5G communication is designed based on Taiwan Semiconductor Manufacturing Company(TSMC)0.13μm Radio Frequency(RF)Complementary Metal Oxide Semiconductor(CMOS)process.The LNA employs self-cascode devices in current-reuse configuration to enable lower supply voltage operation without compromising the gain.This design uses an active feedback amplifier to achieve input impedance matching,avoiding the introduction of resistive negative feedback to reduce gain.A common source(CS)amplifier is used as the input of the low noise amplifier.In order to achieve the low power consumption of LNA,current reuse technology is used to reduce power consumption.Noise cancellation techniques are used to eliminate noise.The simulation results in a maximum power gain of 22.783,the reverse isolation(S12)less than-48.092 dB,noise figure(NF)less than 1.878 dB,minimum noise figure(NFmin)=1.203 dB,input return loss(S11)and output return loss(S22)are both less than-14.933 dB in the frequency range of 2515-4900 MHz.The proposed Ultra-wideband(UWB)LNA consumed 1.424 mW without buffer from a 1.2 V power supply.展开更多
High-temperature pre-stretching experiments were carried out on the AZ31 Mg alloy at 723 K with strain levels of 2.54%,6.48%,10.92%,and 19.2%to alter the microstructure and texture for improving room-temperature forma...High-temperature pre-stretching experiments were carried out on the AZ31 Mg alloy at 723 K with strain levels of 2.54%,6.48%,10.92%,and 19.2%to alter the microstructure and texture for improving room-temperature formability.The results showed that the strain-hardening coefcient increased,while the Lankford value decreased.In addition,the Erichsen values of all pre-stretch sheets were enhanced compared with that of the as-received sheet.The maximum Erichsen value increased from 2.38 mm for the as-received sample to 4.03 mm for the 10.92%-stretched sample,corresponding to an improvement of 69.32%.This improvement was mainly attributed to the gradual increase in grain size,and the(0001)basal texture was weakened due to the activated non-basal slip as the high-temperature pre-stretching strain levels increased.The visco-plastic self-consistent analysis was performed on the as-received and high-temperature pre-stretched samples.Results confrmed the higher activity of the prismatic slip in 10.92%-stretched sample,leading to divergence and weakening of basal texture components.This results in an augmentation of the Schmid factor under diferent slip systems.Therefore,it can be concluded that high-temperature pre-stretching technology provided an efective method to enhance the formability of Mg alloy sheets.展开更多
The hot deformation behavior of a fine-grained Mg–8 Sn–2 Zn–2 Al(TZA822, in wt%) alloy was investigated in the temperature range of 150–350°C and the strain rate of 0.01–10 s^-1 employing thermomechanical si...The hot deformation behavior of a fine-grained Mg–8 Sn–2 Zn–2 Al(TZA822, in wt%) alloy was investigated in the temperature range of 150–350°C and the strain rate of 0.01–10 s^-1 employing thermomechanical simulator. In most of the cases, the material showed typical dynamic recrystallization(DRX) features i.e., a signal peak value followed by a gradual decrease or to reach a steady state. The work hardening rate was found to increase with decreasing temperature and increasing strain rate, while strain rates had great effects on work hardening behavior. Meanwhile, the constitutive analysis indicated that cross-slip of dislocations was likely to be the dominant deformation mechanism. In addition, the processing map at the strain of 0.1–0.7 showed two stability domains with high power dissipation efficiencies and the optimum hot working parameters for the studied alloy was determined to be 350°C/0.01 s^-1 and 350°C/10 s^-1, at which continuous DRX(CDRX) and discontinuous DRX(DDRX) as main softening mechanism. The instability regions occurred at 200–250°C/10 s^-1 and the main flow instability mechanism was twinning and/or flow localization bands, which were prone to induce cracks and caused in-consistent mechanical properties of the alloy.展开更多
基金supported by Natural Science Foundation of Shanxi province (20210302123135,20210302123163)Science and Technology Major Project of Shanxi province (20191102008)+6 种基金Scientific and Technological Achievements Transformation Guidance Special Project of Shanxi province (202104021301022)The Ministry of Science and Higher Education of the Russian Federation for financial support under the Megagrant (No.075-15-2022-1133)the National Research Foundation (NRF) grant funded by the Ministry of Science and ICT (2015R1A2A1A01006795) of Korea through the Research Institute of Advanced MaterialsThe central government guided local science and technology development projects (YDZJSX2021A010)China Postdoctoral Science Foundation (2022M710541)the projects of International Cooperation in Shanxi (201803D421086)Research Project Supported by Shanxi Scholarship Council of China (2022- 038)。
文摘Creep aging forming(CAF) is a potential process used to manufacture large integral components of magnesium(Mg) alloys. The selected stress plays a crucial role in creep aging processes but the mechanism by which stress loading method affects creep aging of Mg alloys is still unclear. In this paper, the microstructural evolution of precipitated phases and precipitation-free zones(PFZ) at grain boundaries with different stress loading modes(unstressed, unidirectional tensile stress, and cyclic stress) at 250 ℃ were investigated along with changes in mechanical properties. The results showed that the addition of stress during aging effectively promoted the precipitation of precipitated phases, while unaffecting grain size. Unidirectional tensile stress caused directional growth of β phase([1010]), as well as rotation of weave towards the basal plane texture, resulting in namely stress orientation effect. Solute atoms diffused in the direction of tensile stress while vacancies moved perpendicular to the direction of tensile stress, resulting in PFZ at grain boundaries(157.06 nm). By contrast, cyclic stresses led to the growth of β phase in three directions([1010], [1100] and [0110]). The solute atoms and vacancies were uniformly distributed in the Mg matrix instead of directional diffusion, effectively reducing the width of PFZ(112.39 nm) at the grain boundary. These features significantly improved the mechanical properties of alloy specimens after cyclic stress creep aging when compared to unidirectional stress creep aging, with yield strength(YS), ultimate tensile strength(UTS), and elongation(EL) enhanced from 171.6 MPa, 305.5 MPa, and 4.4%to 174.8 MPa, 326.3 MPa, and 6.9%, respectively.
基金the Central Government Guided Local Science and Technology Development Projects (YDZJSX2021A010)China Postdoctoral Science Foundation (No.2022M710541)+5 种基金the National Natural Science Foundation of China (51704209,52274397,U1810208)the Projects of International Cooperation in Shanxi (201803D421086)Shanxi Province Patent Promotion Implementation Fund (20200718)Research Project Supported by Shanxi Scholarship Council of China (2022-038)Science and Technology Major Project of Shanxi Province (20191102008,20191102007,20181101008)Taishan Scholars Project Special Fund (2021)。
文摘To investigate the role of pre-twins in Mg alloy sheets during warm planar deformation, the stretch forming is conducted at 200 ℃. Results suggest the formability of the pre-twinned AZ31 Mg alloy sheet is enhanced to 11.30 mm. The mechanisms for the improved formability and the deformation behaviors during the planar stretch forming are systematically investigated based on the planar stress states. The Schmid factor for deformation mechanisms are calculated, the results reveal that planar stress states extremely affect the Schmid factor for {10-12}twinning. The detwinning is activated and the prismatic slip is enhanced in the pre-twinned sheet, especially under the planar extension stress state in the outer region. Consequently, the thickness-direction strain is accommodated better. The dynamic recrystallization(DRX) type is continuous DRX(CDRX) regardless of the planar stress state. However, the CDRX degree is greater under the planar extension stress state.Some twin lattices deviate from the perfect {10-12} twinning relation due to the planar compression stress state and the CDRX. The basal texture is weakened when the planar stress state tends to change the texture components.
基金This work was supported by the National Natural Science Foundation of China(No.50571073)the Ph.D.Programs Foundation of Ministry of Education of China(No.20111402110004)the Natural Science Foundation of Shanxi Province,China(No.2009011028-3,2012011022-1).
文摘Mg97−xZn1Y2Alx alloys with long-period stacking ordered(LPSO)structures were prepared by conventional casting method.The optical microscopy(OM),X-ray diffraction(XRD)and the scanning electron microscope(SEM)equipped with energy dispersive X-ray spectroscopy(EDS)were used to analyze the microstructure of the alloys with different compositions.Immersion test and electrochemical measurement were used to evaluate the corrosion behavior of the alloys at room temperature,and the corrosive medium is 3.5%NaCl aqueous solution.The results showed that,with the increasing aluminum(Al)addition,exceptα-Mg and LPSO phases,new phases also emerged on the grain boundaries.At the same time,the zigzag part of LPSO phases disappeared,and the boundaries between LPSO phases andα-Mg became smooth.Furthermore,the addition of Al to Mg-Zn-Y alloys could hinder the activity of cathodic hydrogen evolution reaction and improve the uniformity and compactness of the protective surface film,thus,enhanced the corrosion resistance of Mg-Zn-Y alloys.
基金the Natural Science Foundation of China(51404166 and 51704209)Natural Science Foundation of Shanxi(201801D121088)the Scientific and Technological Innovation Programs of Higher Education Institutions in Shanxi(2014017 and 201802034).
文摘Texture evolution of an extruded dilute Mg-1Sn-1Zn-1Al alloy was thoroughly investigated based on the twinning and dynamic recrystallization(DRX)behavior via hot compression at a strain rate of 10 s^(-1)and temperature of 225℃.It was found that the types and intensities of the texture are strongly dependent on the fraction of twins and DRX modes as well as regions where sub-grain boundaries(sub-GBs)are intensively accumulated.At the initial stage of deformation,the formation of compression direction(CD)-tilted basal texture was mainly determined by the occurrence of{101^(-)2}extension twins.As the strain increases,the variation in the texture intensity was greatly dominated by the DRX modes but the type of main texture remained unchanged.These findings are of great importance for texture modification of wrought Mg-Sn-based alloys during post-deformation.
基金The authors acknowledge the financial support from the National Science Foundation of China through Grant No.50571073Natural Science Foundation of Shanxi Province through Grant No.2009011028-3.
文摘The effects of Ti additions(0,0.4,0.6,0.8,1.0,1.2 wt.%)on the microstructure and mechanical properties of as-cast and aging Mg-0.4%Zn-1.0%Zr-1.5%Ca(wt.%)alloys were investigated.The results indicated that minor Ti can effectively refine grains,while excessive Ti addition resulted in the grain coarsening.When the content of Ti was 0.8 wt.%,the as-cast alloy exhibited the finest grain size of 39μm which contributed to the optimal mechanical properties with Brinell hardness of 57.9 HB,ultimate tensile strength of 145 MPa and elongation of 3.2%.After T6 heat treatment,the continuous net-like Mg_(2)Ca and Mg_(6)Zn_(3)Ca_(2)phases changed to uniform massive T phases(ternary Mg-Zn-Ca phases)and dispersive halo-like precipitates(Mg_(2)Ca and Mg_(6)Zn_(3)Ca_(2)phases).The ultimate tensile strengths of the alloy at room temperature(RT),175℃and 200℃were correspondingly improved to 182 MPa,169 MPa and 141 MPa,respectively.
基金Shanxi provice scientific facilities and instruments shared service platform of magnesium-based matierals electric impulse aided forming(201805D141005)National Natural Science Foundation of China(51404166,51704209,U1810208)+3 种基金Science and Technology Major Project of Shanxi province(20191102008,20191102007,20181101008)Natural Science Foundation of Shanxi Province(201701D121045)Shanxi Province Science Foundation for Youths(2016021063)The Projects of International Cooperation in Shanxi(201803D421086).
文摘The creep properties of as-cast Mg-9Al-1Si alloy and Mg-9Al-1Si-1SiC composite were compared.The results show that Mg-9A1-lSi-lSiC composite performs a better creep resistance than that of Mg-9Al-1Si alloy at constant temperature and stress(473 K,70MPa).Besides,the creep behavior of Mg-9Al-1 Si-1SiC composite at various temperature from 448 K to 498 K and under stresses of 70-90 MPa were systematically investigated.The Mg-9Al-1 Si-1SiC composite exhibited a stress exponent from 5.5 to 6.9 and the creep activation energy fell within the range of 86-111 kJ/mol.The results showed that the creep mechanism of Mg-9Al-1Si-1SiC composite was mainly attributed to the effects of secondary phase strengthening mechanism and dislocation climb mechanism.
基金This work was financially supported by the National Natural Science Foundation(No.61806088)Jiangsu Province Industry-University-Research Cooperation Project(No.BY2018191)+1 种基金Natural Science Fund of Changzhou(CE20175026)Qing Lan Project of Jiangsu Province.
文摘With the development of the times,people’s requirements for communication technology are becoming higher and higher.4G communication technology has been unable to meet development needs,and 5G communication technology has emerged as the times require.This article proposes the design of a low-noise amplifier(LNA)that will be used in the 5G band of China Mobile Communications.A low noise amplifier for mobile 5G communication is designed based on Taiwan Semiconductor Manufacturing Company(TSMC)0.13μm Radio Frequency(RF)Complementary Metal Oxide Semiconductor(CMOS)process.The LNA employs self-cascode devices in current-reuse configuration to enable lower supply voltage operation without compromising the gain.This design uses an active feedback amplifier to achieve input impedance matching,avoiding the introduction of resistive negative feedback to reduce gain.A common source(CS)amplifier is used as the input of the low noise amplifier.In order to achieve the low power consumption of LNA,current reuse technology is used to reduce power consumption.Noise cancellation techniques are used to eliminate noise.The simulation results in a maximum power gain of 22.783,the reverse isolation(S12)less than-48.092 dB,noise figure(NF)less than 1.878 dB,minimum noise figure(NFmin)=1.203 dB,input return loss(S11)and output return loss(S22)are both less than-14.933 dB in the frequency range of 2515-4900 MHz.The proposed Ultra-wideband(UWB)LNA consumed 1.424 mW without buffer from a 1.2 V power supply.
基金supported by the National Natural Science Foundation of China(Nos.51704209,U1810208)the Central Government Guided Local Science and Technology Development Projects(No.YDZJSX2021A010)+3 种基金China Postdoctoral Science Foundation(No.2022M710541)the Projects of International Cooperation in Shanxi(No.201803D421086)the Shanxi Province Patent Promotion Implementation Fund(No.20200718)the Technological Innovation Programs of Higher Education Institutions in Shanxi(No.201802034).
文摘High-temperature pre-stretching experiments were carried out on the AZ31 Mg alloy at 723 K with strain levels of 2.54%,6.48%,10.92%,and 19.2%to alter the microstructure and texture for improving room-temperature formability.The results showed that the strain-hardening coefcient increased,while the Lankford value decreased.In addition,the Erichsen values of all pre-stretch sheets were enhanced compared with that of the as-received sheet.The maximum Erichsen value increased from 2.38 mm for the as-received sample to 4.03 mm for the 10.92%-stretched sample,corresponding to an improvement of 69.32%.This improvement was mainly attributed to the gradual increase in grain size,and the(0001)basal texture was weakened due to the activated non-basal slip as the high-temperature pre-stretching strain levels increased.The visco-plastic self-consistent analysis was performed on the as-received and high-temperature pre-stretched samples.Results confrmed the higher activity of the prismatic slip in 10.92%-stretched sample,leading to divergence and weakening of basal texture components.This results in an augmentation of the Schmid factor under diferent slip systems.Therefore,it can be concluded that high-temperature pre-stretching technology provided an efective method to enhance the formability of Mg alloy sheets.
基金financially supported by the National Natural Science Foundation of China(Nos.51404166,51704209 and51701060)the Shanxi Scholarship Council of China(No.2014-023)+4 种基金the Scientific and Technological Innovation Programs of Higher Education Institutions in Shanxi(No.2014017)the Shanxi Province Science Foundation for Youths(No.2016021063)the Natural Science Foundation of Hebei Province(No.E2016202130)the Research Foundation from Education Department of Hebei(No.QN2015035)the Outstanding Youth Scholar Science and Technology Innovation Program of Hebei University of Technology(No.2015002)
文摘The hot deformation behavior of a fine-grained Mg–8 Sn–2 Zn–2 Al(TZA822, in wt%) alloy was investigated in the temperature range of 150–350°C and the strain rate of 0.01–10 s^-1 employing thermomechanical simulator. In most of the cases, the material showed typical dynamic recrystallization(DRX) features i.e., a signal peak value followed by a gradual decrease or to reach a steady state. The work hardening rate was found to increase with decreasing temperature and increasing strain rate, while strain rates had great effects on work hardening behavior. Meanwhile, the constitutive analysis indicated that cross-slip of dislocations was likely to be the dominant deformation mechanism. In addition, the processing map at the strain of 0.1–0.7 showed two stability domains with high power dissipation efficiencies and the optimum hot working parameters for the studied alloy was determined to be 350°C/0.01 s^-1 and 350°C/10 s^-1, at which continuous DRX(CDRX) and discontinuous DRX(DDRX) as main softening mechanism. The instability regions occurred at 200–250°C/10 s^-1 and the main flow instability mechanism was twinning and/or flow localization bands, which were prone to induce cracks and caused in-consistent mechanical properties of the alloy.